The Nautilus. 



Vol. XVII. MAY, 1903. No. 1. 



TO OUR READERS. 



With the present issue, the publication office of The Nautilus 

 is changed from the Wagner Institute, Philadelphia, to the Boston 

 Society of Natural History, Boston, Mass. This change is in con- 

 sequence of the appointment of Mu. Johnson, the Business Man- 

 ager and Junior Editor, to the curatorship of the Boston Society. 

 All subscriptions, advertisements and other business communications 

 should hereafter be addressed to Mr. Johnson, at the Boston 

 Society ; while MSS. for publication should be sent to Dr. Pilsbry, 

 at the Academy of Natural Sciences of Philadelphia. Books and 

 papers for review may be sent to either or both of the editors. 



MONTANA SHELLS -PYRAMIDTJLA STRIGOSA. 



MORTON .1. ELR01>. 



The various forms of Pyramidida strigosa give a series of exceed- 

 ingly interesting and widely varied structure. The series found in 

 western Montana shows plainly the result of different environment. 

 The different forms of strigosa vary from the large shells along Flat- 

 head Lake, measuring 24.34 mm. in diameter, to the very small speci- 

 mens described below. On July 15, 1900, the ascent of Sinyaleamin 

 mountain was made. At height of 8,o00 feet an alpine variety was 

 found among the loose rock. There was very little vegetation. No 

 trees were near. They had been left 500 feet below. An occasional 

 scrubby plant and the lichens of the rocks afford the food. Ten days 



